This invention pertains to electrochemical cells and more particularly is concerned with liquid cathode reserve cells.
To prevent parasitic discharge, it is known to keep the electrolyte separate from the other cell components during storage until activation. Cells having this feature are known as reserve cells.
A cylindrical reserve cell disclosed in U.S. Pat. No. 4,517,736 by of Franz Goebel and assigned to GTE Communications Products Corporation. The cell includes a lithium anode, a carbon cathode current collector structure, and a porous separator interposed between the lithium anode and the carbon cathode current collector structure. The carbon cathode current collector structure is pressed against the interior wall of a metal housing and is arranged concentrically within the housing with the separator and lithium anode. The assembly of the lithium anode, carbon cathode current collector structure and separator is then exposed to an electrolytic solution including a reducible liquid cathode solvent and an electrolyte solute dissolved in the reducible cathode solvent. Suitable materials for the reducible cathode solvent and the electrolyte solute are thionyl chloride and lithium tetrachloroaluminate, respectively.
An ampule containing a liquid cell component, i.e., a ready-to-use or concentrated electrolyte solution, is centrally located in the cell, surrounded by the anode. The cell can be stored indefinitely until the cell is activated by breaking the ampule to release its contents.
Upon breaking the ampule, it is necessary for the electrolyte to flow past the anode to reach the porous separator and the carbon cathode collector structure. The anode material is not porous, so a conduit for the liquid cell component must be provided.
In copending application Ser. No. 847,993, filed Apr. 3, 1986, for Electrochemical Cell With Novel Anode Geometry, by Goebel and Batson, there is described a cell wherein the anode is cylindrical with a single turn spiral slot extending between its ends. The slot provides passage for the electrolyte to flow past the anode regardless of the cell's orientation.
The electrodes of these cells are thin and by nature subject to collapse under high forces, such as those encountered during acceleration when fired from a gun or upon activation. Such a collapse would likely result in a short circuit.
Another cylindrical reserve cell is described by Babai et al in U.S. Pat. No. 4,499,160. In the Babai et al cell, a cylindrical metal conductor 5 surrounds a centrally located ampule. In one embodiment, an anode is in contact with the cylindrical metal conductor. The anode is provided with a plurality of small holes said to enhance permeation of the electrolyte upon release. Such holes necessarily reduce the active area of the anode and incur additional manufacturing costs.
An object of the invention is to provide a cell having an anode arrangement capable of withstanding high acceleration forces.